1. Field of the Invention
The present invention relates to a developing apparatus provided with first and second frames, and an assembling method for this apparatus.
2. Related Background Art
An image forming apparatus employing an electrophotographic system includes a frame body for holding a toner containing portion provided to contain toner as developer, a developing portion provided to develop an electrostatic latent image on an image bearing body by using toner, or the like. Such frame body is referred to as a developing frame. Now, a conventional developing frame will be described by taking the example of one disclosed in Japanese Patent Application Laid-Open No. 8-15940, with reference to FIGS. 15 and 16.
A process cartridge shown in FIG. 15 includes a developing frame 100 for containing toner T, a photosensitive drum for carrying a latent image, a developing roller 100c for developing the latent image on the photosensitive drum by using the toner T, a charging roller for uniformly charging the photosensitive drum, cleaning means for removing residual toner on the photosensitive drum, and a gripping member provided in the upper side to be held by a user. The developing frame 100 is composed of a toner developing main body 101, and a toner developing wall member 102. A space formed by coupling both members 101 and 102 together is set as a toner containing portion 100a, and the toner T is fed from a toner supplying opening 110a to the developing roller 100c incorporated as a developer carrying body in a developing chamber 100b. 
For coupling the toner developing frame body 101 and the toner developing wall member 102 to each other, first, both members 101 and 102 are joined together, and end parts 101b and 102c are welded to a toner wall portion 102a included in the joined portions. A developing wall portion 102b corresponding to the developing chamber 100b is not welded to the developing frame body 101 and, in both ends, a toner leakage preventing seal 105 is provided in a non-welded part between the developing wall portion 102b and the toner developer frame body 101. Also, as shown in FIG. 16, end members 103 and 104 are attached to both end parts of a longitudinal direction so as to position both members 101 and 102. In the described example, the members 101 and 102 are welded on one surface (toner wall portion 102a).
There is another conventional constitutional example for coupling both members 101 and 102 together, according to which all the joined portions of the members 101 and 102, i.e., even the developing wall portion 102b, may be welded for coupling. Thus, both members 101 and 102 can be firmly coupled together, preventing any positional shifting or the like even when a twisting force is applied. In this case, the toner leakage preventing seal 105 is not provided in the joined portion of the members 101 and 102 in the developing wall portion 102b. In other words, the members 101 and 102 are welded on two surfaces (the toner wall portion 102a and the developing wall portion 102b).
In the foregoing second conventional example, however, the welding joined portion of the toner developing frame body 101 and the toner developing wall member 102 is positioned in the end part of the developing roller 100c. As shown in FIG. 15, a sealing member 106 for preventing toner leakage is provided in the end part of the developing roller 100c. However, as the welding joined portion may easily become rugged, the welding of the sealing member 106 may become difficult, creating the possibility of deteriorating sealing performance.
Objects of the invention are to provide a developing apparatus capable of enhancing the sealing performance of a sealing member, and an assembling method for this apparatus.
Other objects of the invention are to provide a developing apparatus having substantially no stepped portions on a surface, on which a sealing member is supported, and an assembling method for this apparatus.
Yet other objects of the invention are to provide a developing apparatus advantageous in terms of component and assembling costs, and an assembling method for this apparatus.